1. Field of the Invention
The present invention relates to an image projection apparatus, an image projection method, and a computer-readable storage medium.
2. Description of the Related Art
In an image projection apparatus such as a projector, there arises a distortion of a trapezoidal shape in a projection image which is projected on a projection surface by the image projection apparatus when an inclination angle between the image projection apparatus and the projection surface of a screen and the like is misaligned from a predetermined angle.
Since a focal point distance is short especially in an image projection apparatus which is referred to as “ultra short throw projector” and whose focal point distance is shortened more than conventional techniques, even a slight misalignment in inclination angle causes a significant distortion in a projection image.
For a solution for example, known has been such a technique that an image projection apparatus projects a projection image onto a projection surface, captures the projected projection image by an imaging device such as a camera, calculates correction data for correcting a distortion arising in the projection image based on the captured image, corrects the projection image with the calculated correction data, and projects the corrected projection image onto the projection surface.
However, there is a concern about degradation in image quality such as a lack of partial information of a projection image since it is general in such a technique as explained above to perform image processing such as an image compression and an image expansion in correcting the projection image with correction data.
To deal with this concern, disclosed in Japanese Laid-open Patent Publication No. 2012-199772 is a technique in which an image projection apparatus projects a pattern image onto a projection surface, captures the projected pattern image by an imaging device such as a camera, calculates a movement amount of the image projection apparatus to a position where no misalignment in inclination angle arises based on a gap between the captured image and the pattern image, and displaying the calculated movement amount, for example.
The technique disclosed in Japanese Laid-open Patent Publication No. 2012-199772, however, requires checking that the image projection apparatus is moved for the calculated movement amount, thereby requiring separate measurement equipment that measures the movement amount of the image projection apparatus and resulting in cost increase.
Besides, since most image projection apparatuses whose focal point distance is short like the ultra short throw projector generally project an image backward at an upper part of the apparatus, a user is to perform a positional adjustment of the image projection apparatus while looking up at the pattern image from below. In this case, a direction of a line of sight of the user is not perpendicular to a plane of the pattern image and the pattern image seen by the user shows a particular distortion, so that the user is not able to determine whether or not the distortion, caused by the misalignment of the inclination angle, of the pattern image is resolved without moving to a position from which the user is able to look over an entirety of the pattern image and at which the line of sight of the user becomes perpendicular to the plane of the pattern image, and takes extra efforts.
Therefore, there is a need for an image projection apparatus, an image projection method, and a computer-readable storage medium which enable a positional adjustment of an image projection apparatus that resolves a distortion in a projection image without extra cost and efforts.